Platelet-Rich Plasma Injection: How It Works

Author: Sanjoy Debnath

Platelet-rich plasma (PRP) therapy utilizes a patient's platelets to promote healing. This innovative regenerative technique concentrates the healing properties found naturally in blood to facilitate tissue repair and reduce pain. Let's delve deeper into how PRP injections work and review the evidence supporting their efficacy.

What is PRP?

PRP therapy leverages the healing capacity of platelets, colorless blood cell fragments that play an important role in blood clotting and wound healing. Platelets contain granules packed with growth factors and other proteins known to aid cellular regeneration. When platelets encounter injured tissue, they release these molecules which recruit stem cells and stimulate cell division and protein synthesis at the treatment site.

During a PRP procedure, a sample of the patient's blood is collected and processed to concentrate their native platelets. First, the blood is centrifuged to separate red blood cells from the plasma and buffy coat layer containing platelets and white blood cells. The extracted platelet-rich plasma is about three to five times richer in platelets than baseline blood levels.

The result is a small, autologous volume of plasma highly enriched with growth factors such as platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-β), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and insulin-like growth factor (IGF-1). When injected into damaged tissues, PRP induces local levels of these healing compounds at the affected site to accelerate recovery.

How PRP Injections Work

During a typical PRP treatment session, blood is drawn from the patient's arm through venipuncture. Approximately 1-2 tablespoons are needed for most applications. The blood sample is placed into a special centrifuge which spins the blood at high speeds for around 10 minutes to separate its components.

The upper layer consists of platelet-poor plasma while the lower middle layer called the buffy coat contains a highly concentrated dose of platelets and leukocytes suspended in a small amount of plasma. This PRP concentrate is then isolated from the remaining blood components. The activated PRP is drawn up into a syringe and injected into the injured or painful areas under ultrasound guidance if needed.

Upon exposure to damaged tissue, platelets immediately deploy their granular cargo of growth factors and activate resident stem cells by enhancing cellular replication, neovascularization, and recruitment of macrophages and fibroblasts. The rapid influx of these healing compounds stimulates tissue regeneration and promotes ligament, tendon, muscle, and bone rebuilding. This localized, site-specific release of growth signals occurs without the side effects often seen with systemic administration of pharmacological therapies. Multiple PRP injections are generally needed to achieve optimal treatment outcomes as repeated dosing continues stimulating repair.

Evidence for PRP Efficacy

Substantial research supports the use of PRP injections for orthopedic conditions, wound healing, hair regeneration, and facial rejuvenation applications:

Tendinopathy and Ligament Injuries: A meta-analysis found PRP superior to placebo for elbow tendinopathy. For knee ligament injuries, PRP hastened return to play and augmented healing rates.

Osteoarthritis: Several systematic reviews support PRP injections for knee osteoarthritis pain relief and function enhancement.

Plantar Fasciitis: Multiple clinical trials demonstrate PRP injections aid plantar fasciitis recovery more than corticosteroid shots alone.

Achilles Tendinopathy: A 2016 meta-analysis found PRP more efficient than placebo for midportion Achilles tendinopathy.

Rotator Cuff Injuries: Two major reviews endorse PRP's superiority over placebo for reducing rotator cuff tear symptoms.

Wound Healing: Multiple clinical studies and research reviews support enhanced closure of diabetic foot ulcers, pressure sores, and surgically repaired incisions with PRP therapy.

While less research exists directly comparing PRP to corticosteroid shots, a growing body of evidence suggests PRP injections may yield longer-lasting therapeutic benefits with fewer adverse effects than systemic pharmacological interventions. Further studies continue validating PRP's efficacy compared against placebo, no treatment, and alternative treatments for an expanding range of conditions.

How is PRP Treatment Administered?

Once a patient's blood is processed into a platelet-rich plasma suspension, specialized healthcare providers inject the activated solution directly into injured muscles, tendons, joints, or other damaged tissues in a simple outpatient procedure. A few key points regarding PRP administration:

  • The physician performing the injections will likely use ultrasound guidance for precise deposition of PRP in target structures like knees or elbows.

  • Multiple injections are often needed spaced 1-4 weeks apart as repeated administration enhances healing better than single treatments alone.

  • Patients can normally return to normal daily activities after PRP therapy but more strenuous exercise may need reinstatement gradually as advised by their clinician.

  • Providers well-versed in musculoskeletal medicine like physiatrists, physical therapists, or orthopedic surgeons usually perform the injections.

  • During the session, the platelet concentrate is activated before administration using the patient's thrombin and calcium chloride to trigger degranulation and growth factor deployment.

  • Post-procedure discomfort resembling a "Charlie horse" may occur and usually improves within a day or so. Most patients report little or no pain from the injections themselves.

PRP Therapy Results and Recovery

Following PRP administration, most people feel improvement in their condition within 3-6 months but may continue progressing up to a year post-treatment. For chronic or more acute conditions, results can span:

  • Joint pain: Clinical evidence finds PRP injections efficiently relieve knee, hip, and elbow osteoarthritis pain for 3-6 months in the majority of patients.

  • Tendon injuries: Multiple studies report functional enhancement and pain reduction with Achilles, patellar, or rotator cuff tendinopathies employing PRP therapy.

  • Muscle strains: Most athletes experience an accelerated return to play and sports after PRP for hamstring tears or other muscle injuries, often resuming activities in under 4 weeks.

  • Wound healing: Diabetic ulcers, burn scars, and postsurgical incisions exhibit over 50% improvement within 6 weeks and frequently heal entirely with PRP-augmented treatment plans.

  • Hair loss: Multiple randomized controlled trials support PRP injections in growing thicker, fuller hair over 6 months in both male and female pattern baldness.

The need for repeat injections varies per diagnosis; some patients experience lasting remediation from a single PRP series while others gain optimal benefit from periodic boosters. During recovery, patients may feel minor soreness but serious adverse effects rarely occur.

PRP Applications and Potential Alternatives

As its mechanisms of action become better elucidated, PRP injection indications continue widening. In addition to the uses discussed already, some other explored PRP therapy applications include:

  • Tendon transfers: Several case reports and small trials preliminarily support PRP injections potentially enhancing graft incorporation during tendon transfer surgery.

  • Cardiac issues: Pilot investigations indicate PRP injections may benefit cardiac repair following infarction and improve angina symptoms in ischemic heart disease.

  • Neurological injuries: As a supplement post-stroke, early data hints PRP injections could play a role in limiting neurological decline and scar formation.

  • Dental/oral applications: Case series suggest PRP could accelerate osseointegration of dental implants and assist in the healing of extraction sockets or oral surgery sites.

Potential alternatives to PRP therapy include corticosteroid injections, autologous condition serum injections, hyaluronic acid administration, shockwave therapy, dry needling, or surgical intervention depending upon the targeted indication. No single treatment consistently proves superior for all orthopedic issues and careful analysis of each approach's literature is needed.

PRP injections have a favorable safety profile due in large part to their autologous nature but limited risks include minor bleeding or infection at the injection site. Cost can range between $500-1,500 per session depending on the provider and the exact protocol followed. Insurance coverage varies but some private providers do carry PRP injections making them accessible to more patients.

Summary

In summary, PRP injections harness the body's natural healing mechanisms through platelet-rich plasma concentrated in the patient's blood. When deposited into damaged tissues, platelets expedite regeneration by stimulating stem cell activity and releasing a plethora of growth factors crucial for tissue rebuilding.

Multiple high-quality clinical trials, reviews, and case studies validate PRP therapy's efficacy and safety advantages over systemic pharmacological interventions or conventional injection therapies for joint pain, sports injuries, wound and soft tissue healing, and hair loss applications. Though requiring specialized equipment and healthcare providers, PRP injections represent a promising noninvasive option for orthopedic, surgical, and cosmetic conditions benefitting from endogenous tissue repair enhancement. Additional well-designed studies will help expand PRP utilization and further delineate its most impactful clinical roles. As technology and protocols evolve, PRP injection's healing capacities will likely continue developing as well for future healthcare applications.